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https://github.com/youngyangyang04/leetcode-master.git
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Merge pull request #450 from betNevS/master
增加 0098.验证二叉搜索树 go版 (增加中序遍历解题法)
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@ -376,6 +376,28 @@ func isBST(root *TreeNode, min, max int) bool {
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return isBST(root.Left, min, root.Val) && isBST(root.Right, root.Val, max)
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}
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```
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```go
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// 中序遍历解法
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func isValidBST(root *TreeNode) bool {
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// 保存上一个指针
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var prev *TreeNode
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var travel func(node *TreeNode) bool
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travel = func(node *TreeNode) bool {
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if node == nil {
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return true
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}
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leftRes := travel(node.Left)
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// 当前值小于等于前一个节点的值,返回false
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if prev != nil && node.Val <= prev.Val {
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return false
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}
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prev = node
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rightRes := travel(node.Right)
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return leftRes && rightRes
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}
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return travel(root)
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}
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```
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JavaScript版本
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@ -474,7 +474,7 @@ func traversal(root *TreeNode,history map[int]int){
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}
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```
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计数法BSL(此代码在执行代码里能执行,但提交后报错,不知为何,思路是对的)
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计数法,不使用额外空间,利用二叉树性质,中序遍历
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```go
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/**
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@ -485,41 +485,35 @@ func traversal(root *TreeNode,history map[int]int){
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* Right *TreeNode
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* }
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*/
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var count,maxCount int //统计计数
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func findMode(root *TreeNode) []int {
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var result []int
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var pre *TreeNode //前指针
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if root.Left==nil&&root.Right==nil{
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result=append(result,root.Val)
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return result
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func findMode(root *TreeNode) []int {
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res := make([]int, 0)
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count := 1
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max := 1
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var prev *TreeNode
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var travel func(node *TreeNode)
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travel = func(node *TreeNode) {
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if node == nil {
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return
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}
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travel(node.Left)
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if prev != nil && prev.Val == node.Val {
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count++
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} else {
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count = 1
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}
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if count >= max {
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if count > max && len(res) > 0 {
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res = []int{node.Val}
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} else {
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res = append(res, node.Val)
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}
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max = count
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}
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prev = node
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travel(node.Right)
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}
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traversal(root,&result,pre)
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return result
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}
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func traversal(root *TreeNode,result *[]int,pre *TreeNode){//遍历统计
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//如果BSL中序遍历相邻的两个节点值相同,则统计频率;如果不相同,依据BSL中序遍历排好序的性质,重新计数
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if pre==nil{
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count=1
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}else if pre.Val==root.Val{
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count++
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}else {
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count=1
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}
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//如果统计的频率等于最大频率,则加入结果集;如果统计的频率大于最大频率,更新最大频率且重新将结果加入新的结果集中
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if count==maxCount{
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*result=append(*result,root.Val)
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}else if count>maxCount{
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maxCount=count//重新赋值maxCount
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*result=[]int{}//清空result中的内容
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*result=append(*result,root.Val)
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}
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pre=root//保存上一个的节点
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if root.Left!=nil{
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traversal(root.Left,result,pre)
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}
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if root.Right!=nil{
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traversal(root.Right,result,pre)
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}
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travel(root)
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return res
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}
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```
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@ -255,6 +255,29 @@ func findMIn(root *TreeNode,res *[]int){
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findMIn(root.Right,res)
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}
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```
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```go
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// 中序遍历的同时计算最小值
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func getMinimumDifference(root *TreeNode) int {
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// 保留前一个节点的指针
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var prev *TreeNode
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// 定义一个比较大的值
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min := math.MaxInt64
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var travel func(node *TreeNode)
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travel = func(node *TreeNode) {
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if node == nil {
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return
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}
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travel(node.Left)
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if prev != nil && node.Val - prev.Val < min {
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min = node.Val - prev.Val
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}
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prev = node
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travel(node.Right)
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}
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travel(root)
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return min
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}
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```
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JavaScript版本
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